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Comment by throwawayboise | Hacker News Reader

That's E-ZPass, FasTrak, etc. Also those toll bridges where they take a photo of your license plate and send you a bill that includes a $6 "convenience fee"

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They hide ALPR everywhere. All it takes is a camera. I've seen it on the backside of normal green highway signs, where you can't see it and would never suspect it. The idea is to create a dragnet.

Here in the UK, on public roads, they are legally required to sign post that ANPR[1] is in use in that area, and the cameras have to be easily seen, AND a bright yellow colour.

The shady side of it, is on private property, like car parks, where those rules don't apply.

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[1] Automatic NUMBER plate recognition.

They also pay gig workers to literally just drive drive around in vehicles with ALPR in them. Police cars have them, and they trickle down to parking enforcement. And I am sure the parking officer's gear is sending back more than just cars that have been parked over 30 minutes.

Ohhhh, it's a lot more than that.

You're being tracked by your car and phone bluetooth MAC addresses. That's how the "X minutes to exit Y" signboards work. They time how long it takes to see a particular MAC address appear at the next receiver.

You got a cite for that? I’m not saying it doesn’t exist, but that seems horribly overengineered for what has been traditionally accomplished with tracking the average speed of vehicles using radar or vehicle detectors - they have had these signs long before smart devices were common.

I don't even think it's technically possible. Unless a bluetooth device is in discoverable mode it shouldn't be possible to identify them.

I interviewed at a place that managed traffic light behavior and they had a system to evaluate traffic efficiency by watching traffic flow through the whole area, tracked using ambient Bluetooth signals from phones.

>tracked using ambient Bluetooth signals from phones.

What does this mean? Are they just measuring radio power levels in the 2.4GHz spectrum, and using that to determine whether a car is there or not? Or are they actually somehow capturing bluetooth signals, decoding them, and extracting identifiers (eg. MAC) from them?

It was explained to me as if they track individual cars so I assumed they extract identifiers. I don't know much about BT so I had no reason to question if that was possible. I asked about TPMS as an alternative and they said bluetooth was more reliable since many cars didn't use in-wheel transponders.

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